Code misunderstanding detected:  The fees used in the generation of a txn have absolutely nothing to do with the current block size.

The most common cause of this kind of failure I've seen in the past is when a wallet is contaminated by zillions of very small inputs and ends up selecting so many the the resulting txn is >100KB, which it refuses to issue.

Litecoin carries a patch the sets a minimum value for inputs to be considered in coin selection.